Generally, the widely-used peripheral input device of a computer system includes for example a mouse device, a keyboard device, a trackball device, or the like. Via the keyboard device, characters or symbols can be inputted into the computer system directly. As a consequence, most users and most manufacturers of input devices pay much attention to the development of keyboard devices.
The structures and the functions of a conventional keyboard device 1 will be illustrated as follows. Please refer to FIGS. 1, 2 and 3. FIG. 1 is a schematic top view illustrating the outer appearance of a conventional keyboard device. FIG. 2 is a schematic exploded view illustrating a portion of the keyboard device of FIG. 1. FIG. 3 is a schematic cross-sectional view illustrating the assembled structure of the keyboard device of FIG. 2. For example, the keyboard device as shown in FIGS. 1, 2 and 3 is disclosed in Taiwanese Patent No. TWI512774.
The conventional keyboard device 1 comprises plural keys 10′, a base plate 11 and a membrane circuit board 12. The membrane circuit board 12 comprises plural membrane switches (not shown) corresponding to the plural keys 10′. Each of the plural keys 10′ comprises a keycap 101, at least one scissors-type connecting element 102 and at least one elastic element 103. The scissors-type connecting element 102 is connected between the keycap 101 and the base plate 11. Moreover, the scissors-type connecting element 102 comprises a first frame 1021 and a second frame 1022. The second frame 1022 is pivotally coupled to the first frame 1021. Consequently, the first frame 1021 and the second frame 1022 can be swung relative to each other. The elastic element 103 is arranged between the keycap 101 and the base plate 11. Moreover, the elastic element 103 comprises a contacting part (not shown).
While the keycap 101 of any key 10′ is depressed and moved downwardly relative to the base plate 11, the first frame 1021 and the second frame 1022 of the scissors-type connecting element 102 are switched from an open-scissors state to a stacked state. Moreover, as the keycap 101 is moved downwardly to compress the elastic element 103, the corresponding membrane switch is pushed and triggered by the contacting part of the elastic element 103. Consequently, the keyboard device 1 generates a corresponding key signal. When the key 10′ is no longer depressed, the keycap 101 is moved upwardly relative to the base plate 11 in response to an elastic force of the elastic element 103. Meanwhile, the first frame 1021 and the second frame 1022 are switched from the stacked state to the open-scissors state again, and the keycap 101 is returned to its original position.
The key 10′ further comprises two stabilizer bars 104. Each stabilizer bar 104 comprises a transverse bar part 1041 and two hook parts 1042. The two hook parts 1042 are located at two ends of the transverse bar part 1041, respectively.
The base plate 11 comprises a plate body 112 and plural connecting structures 111. The plate body 112 is located under the membrane circuit board 12. The plural connecting structures 111 are protruded upwardly from the plate body 112 and penetrated through the membrane circuit board 12. Each connecting structure 111 comprises an upper connecting part 1112 and plural lateral connecting parts 1113. The plural lateral connecting parts 1113 are connected with the upper connecting part 1112. Moreover, plural locking holes 1111 are formed between the connecting part 1112, the plural lateral connecting parts 1113 and the plate body 112. The transverse bar part 1041 of the each stabilizer bar 104 is pivotally coupled to the keycap 101 of the key 10′. The two hook parts 1042 of each stabilizer bar 104 are penetrated through the locking holes 1111 of the corresponding connecting structure 111.
Please refer to FIG. 3 again. While the keycap 101 of the key 10′ is moved upwardly or downwardly relative to the base plate 11, the stabilizer bars 104 are moved in the direction D11, the direction D12, the direction D13 or the direction D14, and rotated in the direction D15 or the direction D16. By this design, the key 10′ is kept stable and not inclined while the key 10′ is moved upwardly or downwardly relative to the base plate 11. Moreover, this design is helpful to increase the strength of the keycap 101.
Please refer to FIGS. 2 and 3 again. The plate body 112 of the base plate 11 comprises plural accommodation spaces 114, which are in slot forms. The positions of the accommodation spaces 114 are determined according to movable ranges of the hook parts 1042 of the corresponding stabilizer bars 104. That is, the positions of the accommodation spaces 114 are substantially located under the movable ranges of the hook parts 1042. The membrane circuit board 12 comprises an extension part 125. The accommodation spaces 114 are covered by the extension part 125. While each stabilizer bar 104 is moved with the keycap 101, only the hook parts 1042 of the stabilizer bar 104 are contacted with the extension part 125 of the membrane circuit board 12. In addition, the hook parts 1042 and the extension part 125 are sunken downwardly into the accommodation spaces 114 of the plate body 112. That is, while the stabilizer bar 104 is moved, the stabilizer bar 104 is not directly contacted with the plate body 112 of the base plate 11. Since the stabilizer bar 104 does not directly collide with the plate body 112 of the base plate 11, the sound resulted from the collision will be reduced. In such way, the efficacy of reducing the noise is achieved.
As mentioned above, the plate body 112 of the base plate 11 comprises the slot-form accommodation spaces 114 for reducing the noise, and the extension part 125 of the membrane circuit board 12 is used to cover the accommodation spaces 114 and support the hook parts 1042 of the stabilizer bar 104. However, since the extension part 125 of the membrane circuit board 12 is made of a soft material and there is no supporting structure under the extension part 125, the action of the stabilizer bar 104 is not stable. In other words, the function of stabilizing the key 10′ by the stabilizer bar 104 is largely reduced.
Recently, the trend of designing the keyboard device 1 is toward miniaturization. Consequently, the diameter of the stabilizer bar 104 is gradually reduced. After the hook part 1042 of the stabilizer bar 104 is penetrated through the corresponding locking hole 1111 of the connecting structure 111, the vacant spaces between the hook part 1042 and the upper connecting part 1112 and the plural lateral connecting parts 1113 of the connecting structure 111 become larger. Consequently, while the stabilizer bar 104 is moved with the keycap 101, the hook part 1042 of the stabilizer bar 104 readily collides with the upper connecting part 1112 and the plural lateral connecting parts 1113 to generate a sound. Especially, the sound-reducing design of the conventional keyboard device 1 results in another drawback. After the hook part 1042 is sunken downwardly into the corresponding accommodation space 114 and the hook part 1042 is moved upwardly in response to an elastic force of the extension part 125, the hook part 1042 strongly collides with the upper connecting part 1112 of the connecting structure 111 because of the elastic force. Consequently, the intensity of the sound becomes louder. Generally, the sound from collision is unpleasant noise to the user.
In other words, the conventional keyboard device 1 needs to be further improved.